class MasterSlaveDBRouter(object):    """数据库读写路由"""    def db_for_read(self, model, **hints):        """读"""        return "slave"    def db_for_write(self, model, **hints):        """写"""        return "default"    def allow_relation(self, obj1, obj2, **hints):        """是否运行关联操作"""        return True